U.S. Pat. No. 5,753,153 (Inventor: Choi; Published: 1998 May 19) discloses a control system for clamp-up and mold-break operations of a tie-bar clamping mechanism. The control system can determine and adjust a starting position of a securing/clamping mechanism and a movable mold after each molding operation to achieve greater accuracy.
U.S. Pat. No. 5,773,050 (Inventor: Wohlrab; Published: 1998 Jun. 30) discloses a tool-closure system for an injection-molding machine that uses a threaded spindle to open and close tools, and piston and cylinder units for applying a high-pressure clamping force.
U.S. Pat. No. 5,922,372 (Inventor: Schad; Published: 1999 Jul. 13) discloses a molding-machine platen clamping system that includes columns fixed to a moving platen with teeth at remote end engaged by a hydraulic clamping system (this U.S. patent was reissued on 3 Sep. 2002 as patent U.S. Pat. No. RE 37,827).
U.S. Pat. No. 6,186,770 (Inventor: Ziv-Av; Published: 2001 Feb. 13) discloses a clamping assembly for an injection-molding machine that includes a pair of tie bars with threads which engage with threaded bushings in platens by relative rotation of the tie bar and the platens generated by an actuation system.
U.S. Pat. No. 6,200,123 (Inventor: Mailliet et al; Published: 2001 Mar. 13) discloses a hydraulic-closure unit, in e.g. a pressure injection-molding machine that combines double-acting annular cylinder with breech-action locking which allows relative sliding of a pressure rod and turns to engage inner and outer threads, taking up play and arriving at a force transmission position.
U.S. Pat. No. 6,210,144 (Inventor: Mailliet et al; Published: 2001 Apr. 3) discloses a closure unit for a pressure injection-molding machines, in compact arrangement which also allows free sliding of a moving platen. The closure unit includes double-acting hydraulic cylinders on a fixed platen which act through locking bushes onto tie rods with interrupted threads which are engaged whilst taking up backlash by turning.
U.S. Pat. No. 6,250,905 (Inventor: Mailliet et al; Published: 2001 Jun. 26) discloses a compact injection-molding machine closure unit that has locking bushes on tie bars between fixed and moving platens which engage with threads on bars to absorb backlash and to transmit a closure force from double-acting hydraulic cylinders.
U.S. Pat. No. 6,439,875 (Inventor: Morita et al; Published: 2002 Aug. 27) discloses a clamping apparatus for an injection-molding machine that includes a mechanical ram and a piston between which a chamber is defined for pressure exertion so as to drive the mechanical ram to obtain a mold-locking force.
U.S. Pat. No. 6,719,553 (Inventor: Hehl; Published: 2004 Apr. 13) discloses a slide-bar or C-frame pressure injection molding machine.
U.S. Pat. No. 6,821,463 (Inventor: Di Dio et al; Published: 2004 Nov. 23) discloses clamping of molds in an injection-molding press by supporting tie rods sliding with respect to platens, providing locking bushes for tie rods, a moving platen, and inter-engaging screw-threaded portions of the tie rods and the locking bushes.
U.S. Pat. No. 6,884,057 (Inventor: Dantlgraber; Published: 2005 Apr. 26) discloses an electromechanical tensioning unit that includes two tensioning jaws, a pushing-gear mechanism, and primary and secondary cylinders for moving the tensioning jaws.
U.S. Pat. No. 6,984,121 (Inventor: Fischbach et al; Published: 2006 Jan. 10) discloses a mold-clamping plate for an injection molding machine, that includes a central plate with sleeves at its corners which surround bores for spindles of a spindle drive, and the sleeves are only partially connected to plate.
U.S. Pat. No. 6,971,237 (Inventor: Geiger; Published: 2005 Dec. 6) discloses a servo-actuator for selectively controlling movement of an output member in two directions relative to a frame in a plastic-molding machine, that includes a motor-driven actuator with hydraulic force amplification.
United States Patent Application Number 2005/0170037 A1 (Inventor: Koike et al; Published: 2005 Aug. 4) discloses a die-clamping unit for an injection-molding machine that has a control device that: (i) drives a half-nut positioning servo-motor with the half-nut and a tie bar engaged with each other by an engaging mechanism and that (ii) controls a hydraulic-die clamping unit.
Prior art molding systems require a clamp piston to actively position interrupted teeth of a tie bar for locking and unlocking the tie bar to a platen, and this arrangement may require additional molding-system cycle time, increased cost and increased complexity of individual control valves for each clamp piston. If stroking of a clamp piston is used for positioning interrupted teeth for locking and unlocking a tie bar to a platen, a volume of hydraulic fluid in a clamp cylinder may be more than required for actual clamping stroke and therefore this arrangement may require more hydraulic fluid flow and energy to compress during a clamp-up phase.
It appears that most prior-art molding systems use at least three separate mechanisms, which are: (i) a lock for locking and unlocking a tie bar with a platen, (ii) a mold shut-height adjustment mechanism to adjust for a mold-shut height position when exchanging one mold for another mold, and/or (iii) a clamp piston that is stroked to accommodate the mold shut-height position within a range of a tooth pitch of interrupted teeth of the tie bar. Disadvantageously, by using each of the separate mechanisms in the prior-art molding systems, the following setbacks may be experienced: (i) increased cost, (ii) increased complexity, (iii) reduced reliability and/or (iv) increased cycle time of the molding system.